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13.13.3.3.1.1.9 Method 9: Halogenation

DOI: 10.1055/sos-SD-013-00626

Tomé, A. C.Science of Synthesis, (200413561.

Benzotriazole is rapidly converted into crystalline 1-chloro-1H-1,2,3-benzotriazole (682, X=Cl) by treatment with sodium hypochlorite in aqueous acetic acid (Scheme 248).[‌692‌] Similar reaction with sodium hypoiodite in aqueous sodium hydroxide gives 1-iodo-1H-benzotriazole in 43% yield.[‌687‌] Alternatively 1-iodo-1H-benzotriazole is obtained in 94% yield by treatment of 1-chloro-1H-benzotriazole in dichloromethane with 1 equivalent of iodine.[‌687‌] Similarly, 1-bromo-1H-benzotriazole is prepared in 80% yield by the addition of 1-chloro-1H-benzotriazole to a solution of bromine in dichloromethane.[‌687‌] Addition of sodium hypochlorite to a solution of 4,5,6,7-tetrachloro-1H-benzotriazole in glacial acetic acid, at room temperature, rapidly affords N,4,5,6,7-pentachloro-1H-benzotriazole (because of the extreme insolubility of this compound, the position of the fifth chlorine at N1 or N2 was not assigned unambiguously).[‌687‌]

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References